Sustainability of Water

Question 1

Why is desalination used?

Answer 1

It is used to provide safe and reliable water to expanding populations, particulaly ones most affected by climate change. It is also drought-proof as the ocean will take forever to run out.

Question 2

Describe irrigation

Answer 2

Irrigation, which is the artificial application of water to the land or soil, has been used by humans for thousands of years. It is estimated that around 50% of the world’s agricultural land uses some type of irrigation.

Question 3

Describe drought-resistant crops

Answer 3

GM has been used on wheat to produce crops that are drought resistant. Farmers in drought-affected Kitui, Kenya, saw their yields more than double since they started using drought resistant crops grown from improved (GM) seed varieties. Also look back on your Food notes.

Question 4

Name 3 methods to conserve water in industry

Answer 4

• Replacing water-cooled equipment with air cooled equipment where possible in manufacturing industries.
• Installing water efficient showers, taps and toliet systems in hospitality.
• Reusing and recylcing grey (used) water on processes which do not require clean water.

Question 5

Name 5 methods of cleaning water

Answer 5

• Screening, to remove larger pieces of debris from surface water.
• Coagulaion and flocculation, a coagulant chemical is added to water causing small partcilces to clump together, forming floc. Water is then put through two more filters to remove invisible particles. (rapid gravity (coarse sand) and slow sand (finer sand)
• Sedimentation (large tank allows floc to settle at bottom.)
• Filtration (to remove bacteria, parasites and remaining suspended particles.)
• Disinfection (devloped countries use a small amount of chlorine, developing countries either boil it, use chlroine tablets or biosand filters)

Question 6

Describe 5 methods used in sewage treatment

Answer 6

• Preliminary treatment — screening to remove bulky solids, and grit removal.
• Primary treatment — sedimentation to remove remaining solids. Produces sludge and liquor; sludge is removed and treated, liquor passes to the next stage.
• Secondary treatment: biological oxidation using micro-organisms and aeration removes dissolved and suspended organic matter. Sludge is removed and treated, liquor passes to the next stage.
• Tertiary treatment: filtration, to remove remaining suspended matter and toxins from the liquor, which is now known as effluent.
• Discharge of effluent to river or sea

Question 7

What are the end uses of sewage sludge

Answer 7

• heat treated to remove liquid and kill bacteria, then used as agricultural fertilser.
• turned into sludge cake and used for energy generation through incineration or by drying it into blocks (cake) which can be burned.
• anareobic digestion to generate biogas heating it with bacteria to produce methane. These biogas can be used for heat and electricity generation.